Spacecraft vibration reduction using pulse modulated command input and smart materials

Purpose - To provide an approach to active vibration reduction of flexible spacecraft actuated by on-off thrusters during attitude control for spacecraft designers, which can help them analysis and design the attitude control system. Design/methodology/approach - The new approach includes attitude controller acting on the rigid hub, designed by using pulse-width pulse-frequency modulation integrated with component command technique, and the piezoelectric material elements as sensors/actuators bonded on the surface of the beam appendages for active vibration suppression of flexible appendages, designed by optimal positive position feedback (OPPF) control technique. The OPPF compensator is devised by setting up a cost function to be minimized by feedback gains, which are subject to the stability criterion at the same time, and an extension to the conventional positive position feedback control design approach is investigated. Findings - Numerical simulations for the flexible spacecraft show that the precise attitude control and vibration suppression can be accomplished using the derived vibration attenuator and attitude control controller. Research limitations/implications - Studies on how to control the on-off actuated system under impulse disturbances are left for future work. Practical implications - An effective method is proposed for the spacecraft engineers planning to design attitude control system for actively suppressing the vibration and at the same time quickly and precisely responding to the attitude control command. Originality/value - The advantage in this scheme is that the controllers are designed separately, allowing the two objectives to be satisfied independently of one another. It fulfils a useful source of theoretical analysis for the attitude control system design and offers practical help for the spacecraft designers.